The parents of 3649 Finnish children and adolescents were interviewed in 1980 to evaluate the prevalence of bronchial asthma, allergic rhinitis and atopic dermatitis. The same group was interviewed 6 years later to determine the incidence of new cases of bronchial asthma in the 1980s. Age- and sex-matched samples were taken from three areas, southern, eastern and northern Finland to allow assessment of possible regional differences in prevalences and incidences. The prevalences of atopic eczema, allergic rhinitis and asthma were 1.7%, 6.0% and 4.3%, respectively. These figures are similar to those found in previous studies in Scandinavia and Finland over 10 years ago. The prevalence of atopy was highest (6.4%) in southern Finland, which is the most urbanized area of our country. The prevalence of asthma was highest (3.3%) in northern Finland. This is still low when compared with the incidences in other European countries. THe prevalences of asthma and atopy were lowest in eastern Finland which is the most agrarian area. The incidence of asthma was 1.5 cases/1000 individuals/year, but regional differences were shown.